1 Rattlesnakes -- or rattlers -- are dangerous and venomous. Rattlesnakes are famous for the rattles at the end of their tails. Rattlesnakes' rattles are made up of a series of loosely connected yet interlocking rings. They make a buzzing sound when shaken.2 Rattlesnakes are found in arid areas of the Americas (such as the Great Basin Desert in the U.S.). Rattlesnakes belong to the viper snake family. Like all vipers, rattlesnakes have two long, hollow fangs in their upper jaws. Usually, rattlesnakes and their viper relatives fold them back in their mouths. When vipers are ready to strike (either for catching prey or for self-defense), they open their mouths wide, swing forward their fangs, and give their target a deadly injection of venom!3 Rattlesnakes have a very good sense of smell. By flicking their tongues in and out of their mouths, rattlesnakes are constantly sampling the air. They can pick up the faintest trace of a smell emitted by animals. Yet, aside from their tongues, rattlesnakes have a powerful secret weapon that is guaranteed to leave their victims exposed. Amazingly, rattlesnakes and some viper species have heat-sensitive pits on each side of their flattened, triangular-shaped heads. These pits can detect the slightest change in temperature as a warm-blooded animal draws closer. Aided with these two potent devices, rattlesnakes have no problem tracking down an animal even when it is pitch black.